1. Field of the Invention
This invention relates generally to telecommunications, and, more particularly, to a method and apparatus for reducing false hook detection in a line card.
2. Description of the Related Art
In communications systems, particularly telephony, it is a common practice to transmit signals between a subscriber station and a central switching office via a two-wire bi-directional communication channel. A line card generally connects the subscriber station to the central switching office through a subscriber line. At the subscriber end, a telephonic device may be employed to establish communication with a remote user using the subscriber line. The combination of the telephonic device and the subscriber line is commonly referred to as a subscriber loop.
A line card generally includes at least one subscriber line interface circuit (SLIC) as well as a subscriber line audio-processing circuit (SLAC). The SLIC interfaces with the subscriber loop, and the SLAC interfaces with the SLIC. The SLIC and the SLAC carry out the well-known BORSCHT (Battery feed, Overvoltage protection, Ringing, Supervision, Coding, Hybrid, and Test) functions.
The SLIC of the line card may operate in a variety of states, such as a standby state, active state, and ringing state. Each state may have its own current resolution mode. For example, the standby state may be a high-resolution current mode, while the ringing state may be a low-resolution mode. Switching between the three states may give rise to undesirable transients, partly because of the varying level of currents in the different modes. As a result, the undesirable transients may adversely affect the operation of the SLIC, resulting in false hook detection, for example.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.